Automatic regulator for electric motors.



No. 630,6l8. Patented Aug. 8, I899.

A. T. MARSHALL.

AUTOMATIC REGULATOR FOR ELECTRIC MOTORS (Application filed Aug. 29,1898.) (No Model.) .2 Sheets-Sheet iinesses. 0 nventor. fd q m. a. e? \y43,) 5y

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AUTOMATIC REGULATOR FOR ELECTRIC MOTURS. (Application filedAug. a9,1898.) (No Model.) 2 Sheets-Shuet 2,

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UNITED STATES,

PATENT OFFICE.

Al/l'lERT T. MARSHALL, OF BROOKTON, MASSACHUSETTS AUTOMATIC REGULATORFOR ELECTRIC MOTORS.

SPECIFICATION forming part of Letters Patent N 0. 630,618, dated August8, 1899.

Application filed August 29 1898.

To (LZZ whom it; may concern.-

Be it known that I, ALBERT T. MARSHALL, a citizen of the United States,residing at Brockton, in the county of Plymouth and State ofMassachusetts, have invented a new and useful Automatic Regulator forElectric Motors, of which the following is a specification.

Myinvention relates to an automatic regulater for an electric motor,which has been especially designed for controlling the electric motoractuating the pump of a refrigerating plant.

The object of my present invention is to provide a simple, eflieient,inexpensive, and compact automatic rheostat which is especially adaptedto be combined and controlled by a thermostat.

To these ends my invention consists of the parts and combinations ofparts, as hereinafter described, and more particularly pointed out inthe claims at the end of this specification.

In the accompanying two sheets of drawings, Figure l is a diagrammaticView of a refrigerating plant provided with an automatic regulatorconstructed according to my invention. Fig. 2 is a perspective view ofmy automatic rheostat combined with a thermostat. Fig. 3 isadiagrammatic View illustrating the electrical connections of therheostat. Fig. 4 is a sectional yiew of the same. Figs. 5 and (5 aredetail views of the controllingrpawls and contact-pieces to behereinafter referred to, and Fig. 7 is a sectional plan view of anautomatic rheostat constructed according to my invention.

A refrigerating plant for employing anhydrous ammonia or similarexpansible medin n1 ordinarily comprises a storage-chamber for theliquid refrigerating medium, a coil or worm in which the refrigeratingmedium is allowed to expand into agas, and a pump for condensing the gasback into the form of a liquid, which is returned to the storagechamber.

In a refrigerating plant which employs an electric motor for driving thepump it is extremely desirable to provide for automatically controllingthe motor so that the pump will be run or worked to cause a circulationof the refrigerating medium only at such times as-is necessary and willbe automatically cut Serial No. 689,749 (No model.)

out or its return action stopped when the tie sired temperature has beenreached in the space being refrigerated.

As illustrated diagrammatically in Fig. 1, C designates thestorage-chamber for the liquid refrigerating medium; D, theexpansionvalve, as it is termed, which throttles or allows only smallquantities of the refrigerating medium to pass into the expansion-coilor worm E, from which the ammonia is pumped by means of a pump 13, whichin the construction illustrated is belted from an electric motor A.These parts may be of any ordinary or approved construction and need notbe herein described at length.

As illustrated in Figs. 2 to 7, inclusive, the automatic regulator whichI preferably employ comprises a casing 20, having a bindingpost 21 forthe line-wires and three bindingposts 22, the center one of which isconnected to a thermostat 23, which thermostat 23 may consist of a barof compound material in the ordinary manner. The outside binding-posts22 are connected to adj ustable contact-pieces which cooperate with thethermostatic bar 23 and also to the electrical connections which controlthe contact-arm of the rheostat, as hereinafter explained.

A switch, as S, may be arranged on top of the casing 24, so as to pass acurrent through the stopping or starting connections of the rheostatwhen it is desired to dispense with an automatic control by thethermostatic bar 23. The front of the casing is closed by a plate ofslate or similar material 24, carrying binding-posts 25 andsector-shaped eontact-plates near the center thereof, as here inafterexplained. In order to provide for an automatic action, the contact-armof the rheostat is preferably turned or rotated by means of a train ofclockwork, as shown most clearly in Figs. 4- and 7. As illustratedtherein, this train of clockwork comprises an ordinary clock-spring 30,which through a gear and pinion drives the main shaft 31. A second shaft82 is driven from the main shaft 31 by means of a gear and pinion, and athird shaft carrying a regulating plate orfan 33 is driven by a gear andpinion from the second shaft 32. Loosely splined onto the outer end ofthe main shaft 31 is a block of insulating material, as 34, whichcarries the spring contact-arm 29, which contact-arm 29 is retained inplace by the bridgepiece 27 and has terminals or end pieces cooperatingwith the sector-shaped contact-strips before referred to.

As illustrated most clearly in Fig. 8, the sector-shaped contact-stripsare arranged in two concentric rows, the outer row comprisingcontact-strips 45, 4:50, e6, 47, L70, t8, and lSO. The inner rowcomprises contact-strips 60, 61, and 63.

As shown diagrammatically in Fig. 8, the contact-strips t5 and (31 areinsulated or without electrical connection with the motor, so that whenthe spring contact-arm 29 is in the position illustrated by dotted linesin this figure the current will be shutoff both from the field andarmature of the motor A.

lVhen the spring contact-arm 29 is turned to the right, it will be seenthat an electrical connection will be made with the line-wire throughthe bridge-piece 27 and the spring contact-arm 29, so as to direct thearmature current through the resistance-coils -10 and 50, while at thesame time an electrical connection will be made through the bridge-piece27, the spring contact-arm 29, and contactstrip 60 to inclose thecircuit through the field-magnets of the motor. As the contactarm 29continues to revolve it will be brought successively into engagementwith the contact-strips 4S and t7, thus first cutting out theresistance-coil 50 and then the resistancecoil t9, so that when inengagement with the contact-strip at? the full strength of the currentwill be directed through the armature to drive the motor at full speed.The contact-arm of the rheostat will be maintained in this position aslong as it is desired to run the motor, and when the motor is to be cutout the contact-arm will be started up again to turn in the samedirection.

The contact-strips 4:6 and 4:70 and the contact-strips 50 and 1-80 areconnected together, so that the resistance-coil 19 will be firstintroducedintothearmature-circuit. Thenihe armature-circuit will bedirected through both coils -l9 and 50 and the circuit through thearmature of the motor will be broken, when the contact-arm passes intoengagement with the contact-section'l5.

The sector-shaped contact-section 03 in the inner line of contact-piecesis arranged to introduce a resistance, as 51, into the field-circuit ofthe motor just before the motor is shut off, as I have found that bythis arrangement I am enabled to substantially prevent all sparking.

Any desired construction may be employed for stopping and starting theclockwork so as to turn the spring contact-arm 29-as, for example, thestopping and starting pawls hereina-fter described may be directlyactuated by the expansive force of a thermostat; but in practice Ipreferably control the starting and stopping pawls by suitable magnets.

As illustrated most clearly in Figs. 1: to 6,

notched disks 35 and 36 are secured on the main shaft of the clockwork,and cooperating with the notched disk 35 is a stopping-pawl 39 fornormally stopping the clockwork to shut off the current of the electricmotor and to m aintain the parts of the rheostat in the positionillustrated in Fig. 3. Cooperating with the notched disk 36 is astarting-pawl l0, which when brought into action will allow therheostat-arm to turn until the full strength of the current is turnedonto the motor. The stopping-pawl 39 and starting-pawl t0, asillustrated, are controlled by pins 43 and ii, re spectively, on apivoted armature-lever 49. The armature-lever 2 is controlled bymagnets, as 10 and 11. A shuntfrom the streetcurrent may be sent throughthe magnet 1t), when the circuit is closed by the thermostatic barmoving to the left, as shown in Fig. 1, and when this takes place thepawl 10 will be lifted from its notched disk 36 and the rheostat-armwill be turned so that the parts will assume the position illustrated inthe drawings.

In practice I preferably employ the clockwork itself to form part of thecircuit through the magnet 10, the connections of the magnets 10 and 11with the clockwork being preferably made by insulated springcontact-arms 3S and 59, (see Fig. 5,) which bear upon the notched disks35 and 36, so that when the parts are in the normal position illustratedin the drawings the shunt-circuit through the stopping-magnet 10 will bebroken, as illustrated in Fig. 5.

The thermostatic rod 23 is located in or directly adjacent to the spacebeing refrigerated, and when the temperature rises from the desiredlimit the thermostatic rod will complete a shunt-circuit through themagnet 11, so that the pivoted armature or lever l2 will be shifted fromthe position shown in the drawings,the stopping-pawl 89 will be thrownout by the pin a3, and the starting-pawl 40 will be released to engagethe notch in the stopping-disk, thus lowering the tailpiece of thestopping-pawl into the path of the plate or fan 83 when therheostat-arin has been turned by the clockwork to direct the currentthrough the motor, while at the same time the circuit through the springcontact-arm 5i) and notched disk 36 will be broken. The starting andstopping pawls 39 and 40 are preferably provided with foot-pieces forengaging the fan or plate in this manner, although, if preferred, thenotches in the disk may, if desired, be made of such a shape as to actas ratchet-teeth 'to control the clockwork.

By employing a spring rheostat -arm 29, which is confined in placebeneath the bridgepiece 27, it will be noted that the rheosiatarm willexert a spring-pressure both on its contact sections or feet and on thebridgepiece, and by means of this construction nearly perfect electricalconnections will be made between the bridge-piece 27 and rheostat-arm 29and between the rheostat-arm 211 and the sector-shaped contact-pieceswhich cooperate therewith.

If the street or line current should be shut off or interrupted for anyreason while the motor is running and then be turned on again suddenly,the armature of the motor would be liable to burn out or be injured; anda further object of my invention is to provide a sta tionary cut-outdevice which will automatically shift the rheostat to a stoppingposition whenever the current is broken. To accomplish this purpose, Imay weight or balance the stopping-pawl 39 and provide an electricmagnet for normally holding the same up out of the way while thestreet-current remains uninterrupted, but which will automaticallyrelease said stopping-pawl if the current in the street should bebroken, or I may provide a sup pleinental pawl for accomplishing thispurpose. As illustrated, I may employ a third notched disk 37, securedon the main shaft 31., and cooperating with the notched disk 37 I mayemploy a supplemental pawl al. The supplemental pawl 41 is arranged toengage an arm or pinion projecting from the startingpawl 40. Thesupplemental pawl -11 is normally held up out of the way by a magnet 12,which is included in the circuit from the street-wires, so that as longas the current is turned on and the motor is being driven thesupplemental pawl will not interfere with the action of the stopping andstarting pawls. \Vhcn, however, the street-current is shut oil, themagnet 12 will no longer be energized and the supplemental pawl ll willbe allowed to drop and will engage the pin or projection carried by thestarting-pawl 10, so that the starting-pawl 4C0 will be lifted and theclockwork released to turn the rheostat-arm into stopping position.

I am aware that an automatic rheostat con structed according to myinvention may be controlled by a hand-switch, as S, or by some differentinstrumentality than the thermostatic bar 23, and that it may beemployed in connection with other species of apparatus thanrefrigerating plants. I am also aware that the same may be diiterentlywired or connected; but I prefer to arrange the circuits as hereindescribed and illustrated diagrammatically in Fig. 1, as by connectingthe same in this manner only a shunt-circuit from the street willbe sentthrough the stopping-magnet or the starting-magnet 11, and when eitherof said magnets has been operated its circuit will be automaticallybroken at the spring contact-arms 38 and 59. This arrangement completesa circuit or allows a current to be used only when the motor is running. If preferred, however, the safety-magnet 12 may be located in ashunt-circuit from the line-wires, and it this construction is adopted asmall amount of current will be constantly utilized, but will have theadvantage of not requiring the entire working current to pass throughthe safety-magnet 12.

In this application for patent I do not seek to cover an y specialconstruction of refrigerating apparatus, nor do I seek to cover,broadly, the combination of a refrigerating apparatus with an automaticcombined thermostat and rheostat, as I have claimed this subject-matterin a companion application for patent, filed June t, 1897, Serial No.639,228; but,

Having fully described my invention, what I do claim, and desire tosecure by Letters Patent of the United States, is

1. In an automatic regulator for electric motors, the combination of acontact-arm, means norm ally tending to move said contactarm in onedirection, a thermostat, and means controlled by the thermostat forstopping the contact-arm in different relative positions, substantiallyas described.

2. In a rheostat, the combination of stationary contact-sections, abridge-piece 27, a spring contact-arm 29 confined in position by saidbridge-piece so as to exert a spring-pres sure upon said bridge-pieceand stationary contact-sections, and means for turning said contact-arm,substantially as described.

The combination of a rheostat, comprising a rotary contact-arm,clockwork for turning said contact-arm in one direction, pawls forstopping said clockwork in different relative positions, and athermostat connected to control said pawls, substantially as described.

45. The combination of a rotaryeontact-arm, clockwork for tn rning saidcon tact-arm in one direction, notched disks turned by said clockwork,pawls having foot-pieces for engaging the notched disks, and athermostat connected to control said pawls, substantially as described.

5. The combination of clockwork, comprising a spring 30 operating atrain of gearing, and a fan 33, notched disks and 36, a contact-armcooperating with a plurality of stationary contact-sections, pawls 39and 40 hav ing foot-pieces cooperating with the notched disks 35 and 36and fan 83, a lever 42 having pins controlling said pawls, and athermostat connected to operate said lever 42, substantially asdescribed.

0. The combination of a rotary contact-arm, clockwork for turning saidcontact-arm in one direction, pawls for stopping said clockwork indiiferent relative positions, a pivoted lever or armature for operatingsaid pawls, mag

nets for shifting the armature, a thermostat for energizing saidmagnets, and means controlled by the clockwork for breaking the circuitthrough either magnet when the same has operated, substantially asdescribed.

7. The combination of clockwork, comprising a spring 61 operating atrain of gearing, a fan 33, notched disks 35 and 36, a springcontact-arm 29 cooperating with a plurality of stationarycontact-sections, pivoted pawls 39 and 40 having foot-pieces cooperatingwith the fan 33 and notched disks 35 and 36, a pivoted armature or lever42 controlling said ICC) pawls, magnets 10 and 11 for the pivotedarmature 42, a thermostatic rod 23 for energizing said magnetsrespectively, and spring contact-arms 3S and 39 for interrupting thecircuits through the magnets 12 and 11 respectively, substantially asdescribed.

8. The combination of an electric motor, a rheosta-t, clockworkcontrolling said rheostat, starting and stopping pawls for stopping therheostat in position to drive and stop said motor respectively, and asupplemental weighted pawl connected to throw out the starti n g-pawl topermit the clockwork to turn the rheostat into position to cut out themotor, and a magnet for norm ally holding up said supplemental pawlwhile the motor is running, substantially as described.

In testimony whereof I have hereunto set my hand in the presence of twosubscribing witnesses.

ALBERT T. MARSHALL.

Witnesses:

LoUIs W. SOUTHGATE, lnimr W. Soorncevrn.

